Spring Study- lesson01-03-14

1、Maven环境配置

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>6.0.3</version>
    </dependency>
</dependencies>

2、dao接口、实现类

package com.feijian.dao;

public interface UserDao {
    void getUser();
}

package com.feijian.dao;

public class MySqlDaoImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("MySqlDao方法调用了");
    }
}

package com.feijian.dao;

public class OracleDaoImpl implements UserDao {
    @Override
    public void getUser() {
        System.out.println("OracleDao数据调用");
    }
}

package com.feijian.dao;

public class UserDaoImpl implements UserDao{
    @Override
    public void getUser() {
        System.out.println("UserDao实现类");
    }
}

3、service层接口、实现类（调用setter方法）这样反转，不需要去程序猿更新对象，直接用户调用不同的接口即可

package com.feijian.service;

public interface UserService {
    void getUser();
}

package com.feijian.service;

import com.feijian.dao.UserDao;

public class UserServiceImpl implements UserService {
    private UserDao userDao ;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void getUser() {
        userDao.getUser();
    }
}

 之前每次都是新建一个对象

private UserDao userDao ;
//private UserDao userDao1 = new UserDaoImpl();

第四步：测试

package com.feijian.service;

import com.feijian.dao.MySqlDaoImpl;
import com.feijian.dao.OracleDaoImpl;
import com.feijian.dao.UserDaoImpl;

public class MyTest {
    public static void main(String[] args) {
        UserService myService = new UserServiceImpl();
        ((UserServiceImpl) myService).setUserDao(new OracleDaoImpl());
        myService.getUser();

        ((UserServiceImpl) myService).setUserDao(new MySqlDaoImpl());
        myService.getUser();

        ((UserServiceImpl) myService).setUserDao(new UserDaoImpl());
        myService.getUser();
    }
}